Pressure releasable vehicle pedal assembly

ABSTRACT

A releasable brake pedal system  10  for a vehicle includes a pedal assembly  12  operatively engageable by the driver of the vehicle and a hydraulic actuator assembly  20  for generating pressurized hydraulic fluid for actuating one or more brakes  44 A- 44 D. The pedal system  10  further includes a pressure release valve  30  or 30′ coupled in fluid communication with the pressurized hydraulic fluid. The pressure release valve  30  or  30 ′ is operative to reduce the amount of pressure applied to the brakes  44 A- 44 D during a detected vehicle deceleration indicative of a collision event. The pressure release valve  30  is responsive to a deceleration sensor  40  according to one embodiment, and valve  30 ′ employs a deceleration sensitive inertial mass  76  according to another embodiment. Accordingly, the pedal system  10  reduces forces that may otherwise be transferred to the pedal assembly  12  during a collision.

FIELD OF THE INVENTION

The present invention generally relates to vehicle pedal assemblies, andmore particularly, to a pedal assembly, such as a brake pedal assembly,that is releasable from an operative condition upon imposition of afrontal load to an automotive vehicle.

BACKGROUND OF THE INVENTION

It is generally known in the automotive vehicle design arts that it isdesirable to configure components arranged within the passengercompartment of the vehicle to reduce adverse effects on the vehicleoccupants when subjected to high forces such as are experienced in acollision. While many vehicle interior components facing the vehicleoccupants are designed to minimize the forces during a collision impact,foot pedal assemblies, such as the brake pedal assembly which isgenerally positioned below the instrument panel of the vehicle in thedriver's compartment, may transfer collision caused intrusive forces tothe driver's leg. This is because in a severe frontal collision,deformation of the vehicle dash panel can cause the foot pedal assemblyto move rearward toward the vehicle occupants. In addition, thisrearward translation is often accompanied by some degree of rotationabout a lateral axis of the mounting plane of the pedal assembly.Likewise, the reaction of the occupant in the collision can force theoccupant's legs into the food pedal controls.

Conventional vehicle foot pedal assemblies, such as the brake pedal,clutch pedal, and acceleration pedal assemblies, are commonly assembledtogether in a pedal box assembly which typically is rigidly connected tothe vehicle dash. Foot pedal assemblies employed with hydraulic fluidactuated systems, such as the brake pedal assembly, generally have afoot pedal pad connected to a lever and a piston push rod, with assistfrom a vacuum booster, that compresses a master cylinder which in turngenerates hydraulic fluid pressure. As the brake pedal assembly is movedrearward toward the driver due to collision caused intrusion forces, thehydraulic resistance in the master cylinder applied against the brakepedal assembly may in some instances cause the brake pedal to inflictinjury to the driver's legs. In addition, the hydraulic resistance inthe master cylinder may cause the brake pedal to damage lowerextremities of the occupant due to the reaction of the occupant in acollision, independent of the dash and pedal intrusion forces.

One approach to minimizing such forces during a severe frontal collisionincludes structurally connecting the pedal box assembly to a cowlstructure which remains relatively stable relative to the dash panel.With the pedal box assembly structurally connected to the cowlstructure, relative movement can be made to cause a failure in thestructure supporting the pivots of the pedal box assembly, thus allowingthe pedals to move freely with little constraint following a severefrontal collision. Other approaches have included the use of mechanicalconnections, such as a cable, between the cowl, or some other relativelystable structure, and the pedal box. With these approaches, thedeflection of the pedal assembly relative to the stable structure duringa severe frontal collision is used to actively depress the pedal throughthe action of the aforementioned mechanical connection. However, theaforementioned approaches significantly increase the cost and complexityof the pedal box assembly, and may render the pedal assembliesinoperative following a vehicle collision.

Accordingly, there exists a need, heretofore unfulfilled, for a costefficient device for use in a vehicle, that reduces the intrusion forcesimparted to the occupant by the pedal assembly, and which reduces theforces imparted upon the occupant as the occupant reacts against thepedal assembly during a collision event.

SUMMARY OF THE INVENTION

In accordance with the teachings of the present invention, a releasablepedal system, such as a brake pedal system, for a vehicle is providedwhich reduces forces, such as intrusion forces, applied to the pedalsystem during a vehicle collision. The pedal system includes a pedalassembly that is operatively engageable by an occupant of the vehicle,and an actuator assembly for generating an amount of pressurized fluid.The releasable pedal system further includes a pressure release valvecoupled in fluid communication with the pressurized fluid. The pressurerelease valve is operative to reduce the amount of pressurized fluidduring a detected vehicle deceleration indicative of a vehiclecollision. Accordingly, the releasable pedal system of the presentinvention advantageously reduces the forces transferred to the pedalassembly during a collision.

These and other features, advantages and objects of the presentinvention will be further understood and appreciated by those skilled inthe art by reference to the following specification, claims and appendeddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a diagrammatic view of a brake pedal system having a pressurerelease valve according to one embodiment of the present invention;

FIG. 2 is a flow diagram illustrating a method of reducing hydraulicfluid pressure in the brake system of FIG. 1 during a vehicle collision;

FIG. 3 is a diagrammatic view of a pressure release valve that may beemployed in the brake pedal system according to another embodiment ofthe present invention, and shown in the normally closed position;

FIG. 4 is a diagrammatic view of the pressure release valve of FIG. 3shown in the open position during a vehicle collision; and

FIG. 5 is a diagrammatic view of the pressure release valve of FIG. 3further illustrating the hydraulic fluid flow in the open position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a hydraulic brake system 10 is shown according toone embodiment of the present invention for use in braking a vehicle,such as an automobile. The brake system 10 has a brake pedal assembly 12generally located in the passenger compartment, generally definedrearward of a dash panel in the vehicle. The brake pedal assembly 12includes an elongated pedal 14 pivotally mounted at its upper end to apivotal connection 18 which in turn is generally rigidly secured to thedash panel. Proximate the lower end of the pedal 14 is a pedal pad 16which is configured to be operatively engageable with the foot of thevehicle operator, i.e., driver, to pivot the pedal 14 clockwise as shownin FIG. 1 to actuate the braking system. The brake pedal assembly 12further includes a piston push rod 22 assembled to pedal 14. Push rod 22is axially movable in cooperation with pedal 14 and operatively engagesa brake actuator assembly 20.

The brake actuator assembly 20 is equipped with a vacuum booster 24, abrake master cylinder 26, and a hydraulic fluid storage reservoir 28.Storage reservoir 28 contains a reserve of non-pressurized hydraulicbrake fluid. The vacuum booster 24 provides assist to the piston pushrod 22 to actuate the master cylinder 26. The master cylinder 26, incooperation with the vacuum booster 24, generates a controlled amount ofhydraulic fluid pressure in response to axial movement of piston pushrod 22, which in turn is responsive to operator actuation of pedal pad16, as is generally known in the art. The brake actuator assembly 20made up of vacuum booster 24, master cylinder 26 and reservoir 28, aswell as the brake pedal assembly 12 made up of pedal 14, pedal pad 16and push rod 22, may include conventional brake system assemblies.

The vehicle brake system 10 is shown having four brakes including theright front brake 44A, left front brake 44B, left rear brake 44C, andright rear brake 44D, according to one example. Brakes 44A-44D providefriction braking to brake the corresponding wheels on the vehicle inresponse to the hydraulic fluid pressure generated by the actuatorassembly 20. Each of brakes 44A-44D may include conventional brakeassemblies made up of calipers/cylinders and brake pads as is commonlyknown in the vehicle brake art.

In addition, primary and secondary brake hydraulic circuits 32 and 34provide hydraulic brake fluid flow paths between the master cylinder 26and each of brakes 44A-44D. According to the example shown, hydrauliccircuit 32 is coupled to brakes 44A and 44B, while hydraulic circuit 34is coupled to brakes 44C and 44D. However, it should be appreciated thatone or more hydraulic circuits may employed and may be otherwiseconnected to one or more brakes. For example, the brake circuits couldbe diagonally biased, as is commonly known in the vehicle brake art. Abrake fluid return line 36 is also provided to serve as a return path toallow brake fluid to be expelled from one or both of the brake hydrauliccircuits 32 and 34 and returned to the brake fluid reservoir 28,according to one example.

According to the present invention, a pressure release valve 30 isemployed in fluid communication with one or both of the primary andsecondary brake hydraulic circuits 32 and 34 and is operative to reducethe brake fluid pressure during a vehicle collision. The pressurerelease valve 30 may be connected in series or otherwise tapped into oneor both of hydraulic circuits 32 and 34. The pressure release valve 30may include a solenoid operated, or otherwise actuated, hydraulic valvethat is normally closed to prevent the release of hydraulic brake fluidpressure. It should be appreciated that pressure release valve 30continuously allows hydraulic brake fluid flow between the mastercylinder 26 and each of brakes 44A-44D, and preferably is operable onlyto discharge brake fluid to reduce brake fluid pressure during a vehiclecollision. According to the embodiment shown, pressure release valve 30,when actuated to the open position during a vehicle collision,discharges brake fluid into the brake fluid reservoir 28 via return line36. Accordingly, the discharged brake fluid is recovered and is reusablewithout introducing air into the brake circuits.

Pressure release valve 30 is actuated to the open position to releasebrake fluid pressure in response to a sensed deceleration signal 38indicative of a vehicle collision. The deceleration signal 38 may begenerated by an air bag deceleration sensor 40 or an air bag activationsignal. The air bag deceleration sensor 40, which is generally commonlyavailable on many modern automotive vehicles equipped with air bags,senses vehicle deceleration to detect the occurrence of a vehiclecollision event. The deceleration signal 38 generated by sensor 40 maybe processed via optional signal conditioning circuitry 42, which mayinclude a relay, a microprocessor, or other control device such as anair bag controller that generates an air bag activation signal.

Referring to FIG. 2, a methodology 50 of controlling the vehicle brakesystem 10 shown in FIG. 1 to release brake fluid pressure during avehicle collision is illustrated therein. The brake control methodology50 includes step 52 of sensing a deceleration signal generated by an airbag deceleration sensor. Decision block 54 checks if the decelerationsignal is greater than a crash threshold value and, if not, returns tostep 52 to sense the deceleration signal from the air bag decelerationsensor. If the sensed deceleration signal is greater than the crashthreshold value, methodology 50 proceeds to step 56 to open the pressurerelease valve 30 for a period of time T_(p) to reduce hydraulic brakefluid pressure applied to the vehicle brakes. The temporary reduction ofbrake fluid pressure reduces the amount of intrusion forces that wouldotherwise be transferred to the brake pedal assembly. Decision block 58checks for whether the pressure release time T_(p) has elapsed. Thepressure release time T_(p) may be set to a time interval sufficient tomitigate negative effects on the vehicle occupant. Once the time periodT_(p) has elapsed, methodology 50 proceeds to step 60 to close thepressure release valve 30 to allow the brake system to resume normalbraking operations. Following closure of the pressure release valve,methodology 50 returns back to step 52 to repeat the aforementionedsteps, and therefore may again release brake fluid pressure upondetecting another vehicle collision.

Referring to FIG. 3, a mechanically actuated pressure release valve 30′is illustrated which may be employed in place of the solenoid actuatedvalve 30 and air bag deceleration sensor 40 with signal conditioningcircuitry 42 described above, according to a second embodiment of thepresent invention. The mechanically actuated pressure release valve 30′has a built-in movable mass deceleration sensing mechanism that sensesdeceleration of the vehicle indicative of the imposition of a frontalload during a collision, and automatically opens the hydraulic fluidpath between at least one of the primary and secondary brake hydrauliccircuits 32 and 34 to the return line 36 to thereby reduce the amount ofhydraulic fluid pressure applied to the vehicle brakes.

The pressure relief valve 30′ has a housing 70 formed with an inlet port72 coupled to one of the brake hydraulic circuits, such as primarycircuit 32, and a pressure release outlet port 74 that is shown coupledto return line 36. Housing 70 defines a container which houses a movableinertial mass 76. Inertial mass 76 is preferably cylindrical and has apair of O-ring seals 78 and 80 spaced apart from each other on oppositeends of inertial mass 76 to define a fluid path 82 therebetween.Inertial mass 76 is movable along axis 88 which is substantially alignedwith the longitudinal axis of the vehicle. Disposed between one end ofhousing 70 and one end of inertial mass 76 is a coil spring 84 and astop member 86. Spring 84 biases the inertial mass 76 towards a normallyclosed position to prevent brake fluid flow between the inlet port 72and outlet port 74.

Inertial mass 76 is slidably movable along the axis 88 upon experiencinga sufficient amount of deceleration along the axis 88, which isgenerally indicative of a severe frontal collision of the vehicle.During a vehicle collision event, inertial mass 76 slidably moves fromthe normally closed position to a pressure release open position inwhich fluid path 82 is in fluid communication with both inlet port 72and outlet port 74 as is shown in FIG. 4. The travel of inertial mass 76to the fully open valve position is limited by stop member 86. Inertialmass 76 remains in the open valve pressure release position as long asthe vehicle deceleration is of a sufficient amount. Once the vehicledeceleration decreases below the sufficient amount, inertial mass 76 isbiased back towards its normally closed position to prevent furtherdischarge of hydraulic brake fluid via outlet port 74. The pressurerelease valve 30′ may serve to provide variable pressure release inwhich the amount of hydraulic fluid pressure released is a function ofthe vehicle deceleration. Accordingly, a greater vehicle decelerationmay result is increased pressure release.

The pressure release fluid flow path through valve 30′ in the open valveposition is further shown in FIG. 5. With the valve 30′ open, hydraulicbrake fluid is released from brake hydraulic circuit 32 via a fluid flowpath through inlet port 72, fluid flow path 82, to outlet port 74, whereit may be discharged to the brake fluid reservoir 28 via return line 36.While brake fluid pressure is released from hydraulic circuit 32 viareturn line 36, it should be appreciated that the hydraulic brake fluidpressure may be released from one or both of hydraulic circuits 32 and34 and discharged through other fluid paths.

Accordingly, the brake pedal assembly advantageously is at leastpartially released upon imposition of a detected frontal load to thevehicle. While the present invention has been described herein inconnection with reducing forces, such as intrusion forces, transferredthrough a hydraulic brake pedal assembly during a vehicle collision, itshould be appreciated that the present invention may be used with othertypes of pedal assemblies to minimize adverse affects on the vehicleoccupants. For example, the present invention may be used to reduce suchforces transferred through a hydraulic clutch assembly pedal.

It will be understood by those who practice the invention and thoseskilled in the art, that various modifications and improvements may bemade to the invention without departing from the spirit of the disclosedconcept. The scope of protection afforded is to be determined by theclaims and by the breadth of interpretation allowed by law.

The invention claimed is:
 1. A releasable pedal system for an automotivevehicle, said system comprising: a pedal assembly including a pedal padoperatively engageable by a vehicle operator; an actuator assembly forgenerating an amount of pressurized fluid responsive to the pedalassembly; and a pressure release valve coupled in fluid communicationwith the pressurized fluid and operable to release pressurized fluid toa fluid supply reservoir so as to reduce the amount of pressurized fluidin response to detecting a vehicle collision, wherein said pressurerelease valve further comprises: an inertial mass that is movable inresponse to deceleration to open a fluid path to reduce the amount ofpressurized fluid; a housing having an inlet port and an outlet port,said inertial mass disposed within the housing; and a spring disposed insaid housing and biasing the inertial mass to a closed valve position.2. The system as defined in claim 1, wherein said pressure release valvefurther comprises first and second seals disposed between said inertialmass and said housing, and wherein said first seal is spaced from saidsecond seal to define a fluid flow path therebetween.
 3. A releasablebrake pedal system for an automotive vehicle, said system comprising: abrake pedal assembly including a pedal pad operatively engageable by avehicle operator; a hydraulic brake actuator assembly for generating anamount of pressurized hydraulic fluid responsive to the brake pedalassembly; a brake responsive to said pressurized hydraulic fluid forgenerating braking force; and a pressure release valve coupled in fluidcommunication with the pressurized hydraulic fluid and operable torelease pressurized hydraulic fluid to a fluid supply reservoir so as toreduce the amount of pressurized hydraulic fluid in response todetecting a vehicle collision, wherein said pressure release valvefurther comprises: an inertial mass that is movable in response todeceleration to open a fluid path to reduce the amount of pressurizedhydraulic fluid; a housing having an inlet port and an outlet port, saidinertial mass disposed within the housing; and a spring disposed in saidhousing and biasing the inertial mass to a closed valve position.
 4. Thesystem as defined in claim 3, wherein said pressure release valvefurther comprises first and second seals disposed between said inertialmass and said housing, and wherein said first seal is spaced from saidsecond seal to define a fluid flow path therebetween.
 5. A method ofcontrolling the fluid pressure in a pedal system having a pedal assemblyin a vehicle, said method comprising the steps of: generating an amountof pressurized fluid in response to actuation of a pedal assembly;detecting vehicle deceleration indicative of a collision; and reducingthe amount of pressurized fluid by releasing pressurized fluid to afluid supply reservoir in response to said detected vehicle decelerationto reduce collision caused intrusion force transferable to the pedalassembly, wherein said step of reducing the amount of pressurized fluidpressure comprises controlling a valve including moving a spring biasedinertial mass.